1. Field of the Invention
The invention relates generally to methods for the treatment of neoplastic diseases and, more specifically, to an immunotherapeutic agent comprising a prostate-associated-antigen in conjunction with a chitosan-based adjuvant and its use in the treatment of prostatic carcinoma.
2. Related Technology
Prostatic carcinoma is one of the most common malignancies of men and a leading cause of death in this population. Worldwide it is an important public health concern as over a quarter of a million new cases were diagnosed in 1985 alone. Within the United States, it was predicted that for 1994, 38,000 individuals would succumb to prostate cancer, while in the countries of the European Union it was predicted the disease would account for more than 35,000 deaths. If detected at an early stage, prostate cancer is potentially curable. Its relatively slow growth and androgen dependence distinguish it from most other carcinomas. The disease exhibits an improved prognosis when detected in an early stage, although a majority of cases are diagnosed at later stages, where metastasis of the primary tumor has already occurred. Five year survival rates for patients with prostate cancer range from 88% for those with localized disease to 29% for those with metastatic disease.
Present treatments for prostatic carcinoma include simply monitoring the disease, to radical prostatectomy, radiation therapy, or hormonal therapy. Simple monitoring of the disease is advocated as a reasonable approach for some patients with prostate cancer. Although untreated prostate cancer continues to grow, it may do so quite slowly. Specifically, the growth of the cancer may be slow enough that it causes no problems in a particular individuals lifetime, even if left untreated. While no one can predict exactly how long it will take for a specific cancer to spread or how long a particular individual's lifespan would be, unless an individual is expected to live at least 10 years, simply monitoring with no immediate treatment may be appropriate when the cancer is small and of low grade. If the prostatic cancer is of a higher grade and thus more aggressive then the cancer may be a significant threat to life or health within 10 years and therefore a more aggressive approach to management would be warranted.
Surgery performed for treatment of localized prostate cancer is referred to as a radical prostatectomy. Through an incision in the lower abdomen or below the scrotum, the entire prostate and seminal vesicles are removed. When the carcinoma is confined within the tissues removed during surgery, a radical prostatectomy completely alleviates localized prostate cancer. Such surgery is of little therapeutic value once the cancer has metastasized to the areas surrounding the prostate as well as distant areas of the body. Further, such surgery may leave the individual permanently impotent.
As an alternative to surgery, radiation therapy may be indicated. Specifically, radiation is recommended for men in whom the disease has spread outside of the prostate capsule (and thus making surgery more difficult) but is still localized within the tissues surrounding the prostate capsule. Side effects such as hair loss and lethargy after irradiation have been well documented.
Another form of treatment for prostatic carcinoma involves hormone therapy. Specifically and as prostate cancer has been shown to be under the trophic influence of androgen hormones, androgen deprivation may often produce a regression of the disease and improvement of symptoms. The goal of androgen deprivation is to achieve castration levels of testosterone and dihydrotestosterone. This goal is usually attained by one of four methods: (1) surgical castration (orchiectomy); (2) administration of exogenous estrogens such as diethylstilbestrol (DES); (3) use of analogs of luteinizing hormone-releasing hormone (LHRH) that inhibit the release of pituitary gonadotropins; or (4) the use of anti-androgens, such as flutamide, that block the action of androgens at target tissues. Hormonal therapy is usually used when there is evidence that the cancer has spread beyond the prostate. It is important to note that hormonal therapy is not considered curative. Specifically, the cancer eventually becomes resistant to hormone deprivation and continues to grow. Further, it has been noted in most patients receiving anti-androgen therapy, such therapy will result in the disease becoming hormone independent.
In view of the limitations of the current therapeutic approaches to the treatment of prostatic carcinoma, there remains a need for a more suitable treatment that could be used to alleviate prostate cancer (either localized or metastasized) that is neither invasive nor produces the unwanted side effects of the currently available treatments.